Simple PHP function to generate a random apha-numeric code with only readable characters

randomCode.php

<?php

/*
 * Simple PHP function to generate a random apha-numeric code with only readable characters
 */
function randomCode($length=4) {

   /* Only select from letters and numbers that are readable - no 0 or O etc..*/
   $characters = "23456789ABCDEFHJKLMNPRTVWXYZ";

   for ($p = 0; $p < $length; $p++) 
   {
       $string .= $characters[mt_rand(0, strlen($characters)-1)];
   }

   return $string;

}

?>

I've forked your little function and added a possibility to get an array back with a desired amount of unique random codes. You find it here: https://gist.github.com/NoTeefy/fb830a3b385b2eb3bc58